U.S. patent application number 15/470251 was filed with the patent office on 2017-11-16 for methods and apparatus for forming a glass ribbon.
The applicant listed for this patent is CORNING INCORPORATED. Invention is credited to Allan Mark Fredholm.
Application Number | 20170327401 15/470251 |
Document ID | / |
Family ID | 51298990 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170327401 |
Kind Code |
A1 |
Fredholm; Allan Mark |
November 16, 2017 |
METHODS AND APPARATUS FOR FORMING A GLASS RIBBON
Abstract
A roll forming apparatus includes at least one forming roll
being spaced from a forming body to define a gap. The forming roll
includes a working zone portion having a working zone surface with
a length extending along a rotation axis of the forming roll and a
thermal resistance boundary extending at an acute angle relative to
the rotation axis. In further examples, methods include the step of
feeding a stream of molten glass through the gap to form a glass
ribbon including a formed thickness. The thermal resistance
boundary facilitates substantial uniform radial expansion of the
working zone surface relative to the rotation axis across the
length of the working zone surface in response to heating of the
working zone portion by the molten glass.
Inventors: |
Fredholm; Allan Mark;
(Vulaines sur Seine, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING INCORPORATED |
CORNING |
NY |
US |
|
|
Family ID: |
51298990 |
Appl. No.: |
15/470251 |
Filed: |
March 27, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14334852 |
Jul 18, 2014 |
9643872 |
|
|
15470251 |
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|
61858295 |
Jul 25, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03B 13/16 20130101;
C03B 13/04 20130101 |
International
Class: |
C03B 13/04 20060101
C03B013/04; C03B 13/16 20060101 C03B013/16 |
Claims
1-16. (canceled)
17. A method of forming a glass ribbon with at least one forming
roll and a forming body spaced to define a glass forming gap
between the forming roll and forming body, wherein the forming roll
comprises a working zone portion comprising a working zone surface
including a length extending along a rotation axis of the forming
roll, wherein the forming roll includes a thermal resistance
boundary extending at an acute angle relative to the rotation axis
of the forming roll, the method comprising the steps of: (I)
supplying a stream of molten glass; and (II) feeding the stream of
molten glass through the gap to form a glass ribbon including a
formed thickness, wherein the thermal resistance boundary
facilitates substantial uniform radial expansion of the working
zone surface relative to the rotation axis across the length of the
working zone surface in response to heating of the working zone
portion by the molten glass.
18. The method of claim 17, wherein the thermal resistance boundary
of step (II) is provided as a frustoconical end surface of the
working zone portion.
19. The method of claim 17, wherein the thermal resistance boundary
of step (II) is provided as a plurality of bores spaced radially
about the rotation axis of the forming roll.
20. The method of claim 17, wherein the thermal resistance boundary
of step (II) is provided as a frustoconical groove defined in the
forming roll.
21. The method of claim 20, further comprising the step of
strengthening the frustoconical groove with a plurality of strength
elements positioned within the groove.
22. The method of claim 17, further comprising the step of cooling
the forming roll with a fluid.
23. The method of claim 22, wherein the step of cooling includes
flowing the fluid through a cooling passage extending along the
rotation axis of the forming roll.
24. The method of claim 22, wherein the step of cooling includes
flowing the fluid against an internal central portion of the
forming roll to facilitate substantial uniform expansion of the
working zone surface across the length of the working zone surface
in response to heating of the working zone portion by the molten
glass.
25. The method of claim 17, further comprising the step of
directing heat to outer peripheral edges of the working zone
portion to facilitate substantial uniform expansion of the working
zone surface across the length of the working zone surface in
response to heating of the working zone portion by the molten
glass.
26. The method of claim 17, wherein the acute angle is from about
30.degree. to about 60.degree..
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn.119 to U.S. Provisional Application Ser. No.
61/858,295, filed on Jul. 25, 2013, the content of which is relied
upon and incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates generally to methods and
apparatus for forming a glass ribbon and, more particularly, to a
methods and apparatus for forming a glass ribbon with at least one
forming roll and a forming body spaced to define a glass forming
gap.
BACKGROUND
[0003] Rolled sheet glass is typically formed using a pair of
forming rolls. However, conventional glass roll forming machines
that employ forming rolls typically produce glass ribbon that does
not have a high precision of dimensional uniformity (e.g. thickness
uniformity within +/-0.025 mm) and are unable to form thin glass
ribbon below 2-3 mm in thickness. One factor that contributes to
this lack of precise thickness control is the non-uniform radial
thermal expansion of the forming rolls that are being heated by the
stream of molten glass that is formed into the glass ribbon.
[0004] FIG. 1 illustrates a schematic view of two conventional
forming rolls 101, 103 that are not necessarily drawn to scale for
clarity. As show, the forming rolls are spaced from each other to
define a glass forming gap 105 for receiving a stream of molten
glass 107. The forming rolls 101, 103 may expand radially in a
non-uniform manner due to heating from the stream of molten glass
107 (which may be about 1000.degree. C. or higher). For example, as
indicated by dashed lines 109a, 109b, heating of the forming rolls
101, 103 by the stream of molten glass 107 can cause a working zone
surface of each of the forming rolls to expand radially from the
corresponding rotation axis in a non-uniform manner across the
length of the working zone surface. The non-uniform radial
expansion occurs since the central portions of the forming rolls
101, 103 are being raised to a higher temperature than the
corresponding end portions of the forming rolls 101, 103. Due to
the non-uniform radial expansion, glass ribbon formed by the
forming rolls may consequently have a relatively thin central
portion when compared to the outer opposite edges of the glass
ribbon.
[0005] There is a desire to provide forming rolls that may be used
to form a glass ribbon with a thickness profile that is not
substantially varied due to radial expansion of the forming rolls
when heated.
SUMMARY
[0006] The following presents a simplified summary of the
disclosure in order to provide a basic understanding of some
example aspects described in the detailed description.
[0007] In a first aspect, a roll forming apparatus includes a glass
feed device for supplying a stream of molten glass and at least one
forming roll being spaced from a forming body to define a glass
forming gap between the forming roll and the forming body for
receiving the stream of molten glass to form a glass ribbon having
a formed thickness. The forming roll includes a working zone
portion that comprises a working zone surface for engaging the
stream of molten glass. The working zone surface includes a length
extending along a rotation axis of the forming roll. The forming
roll further includes a thermal resistance boundary extending at an
acute angle relative to the rotation axis of the forming roll.
[0008] In one example of the first aspect, the thermal resistance
boundary is configured such that the working zone surface expands
radially from the rotation axis in a substantially uniform manner
across the length of the working zone surface as a temperature of
the working zone portion is increased from a first temperature to a
second temperature.
[0009] In another example of the first aspect, the thermal
resistance boundary comprises a frustoconical end surface of the
working zone portion.
[0010] In yet another example of the first aspect, the thermal
resistance boundary comprises a plurality of bores spaced radially
about the rotation axis of the forming roll.
[0011] In still yet another example of the first aspect, the
thermal resistance boundary comprises a frustoconical groove
defined in the forming roll. For example, the frustoconical groove
can be provided with one or more strength elements positioned
within the groove.
[0012] In yet another example of the first aspect, the forming roll
includes a cooling passage configured to provide fluid cooling to
the forming roll.
[0013] In still yet another example of the first aspect, the roll
forming apparatus further comprises at least one pair of gap rings,
wherein the forming roll and forming body are spaced by the pair of
gap rings to define the glass forming gap.
[0014] In another example of the first aspect, the pair of gap
rings are mounted to the working zone portion of the forming
roll.
[0015] In yet another example of the first aspect, the acute angle
is from about 30.degree. to about 60.degree..
[0016] The first aspect may be carried out alone or with one or any
combination of the examples of the first aspect discussed
above.
[0017] In a second aspect, a forming roll comprises a working zone
portion comprising a working zone surface for engaging a stream of
molten glass. The working zone surface includes a length extending
along a rotation axis of the forming roll. The forming roll further
includes a frustoconical groove defined in the forming roll and
extending at an acute angle relative to the rotation axis of the
forming roll.
[0018] In one example of the second aspect, the frustoconical
groove is configured such that the working zone surface expands
radially from the rotation axis in a substantially uniform manner
across the length of the working zone surface as a temperature of
the working zone portion is increased from a first temperature to a
second temperature.
[0019] In another example of the second aspect, the forming roll
further comprises a cooling passage configured to provide fluid
cooling to the forming roll.
[0020] In still another example of the second aspect, the forming
roll further comprises at least one gap ring mounted to the working
zone portion.
[0021] In yet another example of the second aspect, the acute angle
is from about 30.degree. to about 60.degree..
[0022] In another example of the second aspect, the frustoconical
groove extends a depth into the working zone surface that is within
a range of from about 50% to about 85% of a radius of the forming
roll.
[0023] The second aspect may be carried out alone or with one or
any combination of the examples of the second aspect discussed
above.
[0024] In a third aspect, a method is provided for forming a glass
ribbon with at least one forming roll and a forming body spaced to
define a glass forming gap between the forming roll and forming
body. The forming roll includes a working zone portion comprising a
working zone surface having a length extending along a rotation
axis of the forming roll. The forming roll further includes a
thermal resistance boundary extending at an acute angle relative to
the rotation axis of the forming roll. The method comprises the
steps of (I) supplying a stream of molten glass and (II) feeding
the stream of molten glass through the gap to form a glass ribbon
including a formed thickness. The thermal resistance boundary
facilitates substantial uniform radial expansion of the working
zone surface relative to the rotation axis across the length of the
working zone surface in response to heating of the working zone
portion by the molten glass.
[0025] In one example of the third aspect, the thermal resistance
boundary of step (II) is provided as a frustoconical end surface of
the working zone portion.
[0026] In another example of the third aspect, the thermal
resistance boundary of step (II) is provided as a plurality of
bores spaced radially about the rotation axis of the forming
roll.
[0027] In yet another example of the third aspect, the thermal
resistance boundary of step (II) is provided as a frustoconical
groove defined in the forming roll. For example, the method can
include the first step of strengthening the frustoconical groove
with a plurality of strength elements positioned within the
groove.
[0028] In another example of the third aspect, the method further
comprises the step of cooling the forming roll with a fluid. For
example, the step of cooling can include flowing the fluid through
a cooling passage extending along the rotation axis of the forming
roll. In another example, the step of cooling can include flowing
the fluid against an internal central portion of the forming roll
to facilitate substantial uniform expansion of the working zone
surface across the length of the working zone surface in response
to heating of the working zone portion by the molten glass.
[0029] In another example of the third aspect, the step of
directing heat to outer peripheral edges of the working zone
portion to facilitate substantial uniform expansion of the working
zone surface across the length of the working zone surface in
response to heating of the working zone portion by the molten
glass.
[0030] In yet another example of the third aspect, the acute angle
is from about 30.degree. to about 60.degree..
[0031] The third aspect may be carried out alone or with one or any
combination of the examples of the third aspect discussed
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] These and other aspects are better understood when the
following detailed description is read with reference to the
accompanying drawings, in which:
[0033] FIG. 1 is a schematic representation depicting the expansion
of two conventional forming rolls;
[0034] FIG. 2 is a perspective view of an example roll forming
apparatus comprising a forming roll spaced from a forming body;
[0035] FIG. 3 is an end view of the example roll forming apparatus
of FIG. 2;
[0036] FIG. 4 is a cross-sectional view of the example roll forming
apparatus taken along line 4-4 in FIG. 2;
[0037] FIG. 5 is a perspective view of another example forming
roll;
[0038] FIG. 6 is a cross-sectional view taken along line 6-6 of
FIG. 5;
[0039] FIG. 7 is a side-view of yet another example forming
roll;
[0040] FIG. 8 is a cross-sectional view along frustoconical planes
8-8 of FIG. 7;
[0041] FIG. 9 is a perspective view still another example forming
roll; and
[0042] FIG. 10 is a cross-sectional view along line 10-10 of FIG. 9
showing the forming roll in use.
DETAILED DESCRIPTION
[0043] Examples will now be described more fully hereinafter with
reference to the accompanying drawings in which example embodiments
are shown. Whenever possible, the same reference numerals are used
throughout the drawings to refer to the same or like parts.
However, aspects may be embodied in many different forms and should
not be construed as limited to the embodiments set forth
herein.
[0044] Roll forming apparatus of the disclosure can be useful to
produce glass ribbon that may be subsequently separated into glass
sheets for various applications. For example, the glass sheets can
be used to manufacture liquid crystal displays (LCDs),
electrophoretic displays (EPD), organic light emitting diode
displays (OLEDs), plasma display panels (PDPs) or other
devices.
[0045] Turning to FIGS. 2-4, one example roll forming apparatus 201
can comprise a glass feed device 203 for supplying a stream of
molten glass 205. As shown in FIG. 2, the glass feed device 203 can
comprise a fish tail slot feed although other glass feed devices
may be provided in further examples. For instance, the glass feed
device can comprise a fusion down draw apparatus, a fusion up draw
apparatus, a redraw apparatus or other glass feed devices that may
supply a stream of molten glass 205.
[0046] As shown, the roll forming apparatus 201 comprises at least
one forming roll 207 spaced from a forming body 209. The forming
roll and forming body can comprise various alternative refractory
materials (e.g., ceramic, platinum, etc.). The materials used to
manufacture the forming roll and forming body are capable of
forming molten glass into a glass ribbon while maintaining the
structural integrity of the forming roll and forming body.
Moreover, as the forming roll and forming body will be contacting
the major surfaces of the formed glass ribbon, the forming roll and
forming body should be made from a material that will not damage or
otherwise contaminate the major surfaces of the formed glass
ribbon. For instance, the forming body can be made from various
metallic alloys (e.g., stainless steel, nickel alloys).
[0047] The forming roll 207 and forming body 209 can define a glass
forming gap 211 between the forming roll 207 and the forming body
209 for receiving the stream of molten glass 205. As shown in FIGS.
2-4, the forming body 209 can comprise a forming roll that may be
identical or different than the forming roll 207. Although not
shown, further examples may provide the forming body 209 as another
member that is not identical or similar to the forming roll 207.
For example, the forming body 209 may comprise a member (rotatable
or nonrotatable) that may cooperate with the forming roll 207 to
define the glass forming gap 211. A glass ribbon 213 can be formed
as the stream of molten glass 205 passes through the forming gap
211 between the forming roll 207 and forming body 209. The glass
ribbon 213 can be formed with a thickness T (see FIG. 3) that
corresponds to a width W (see FIG. 4) of the glass forming gap
211.
[0048] As shown in FIGS. 2 and 4, the forming roll 207 includes a
working zone portion 215 that comprises a working zone surface 217
for engaging the stream of molten glass 205. The working zone
surface 217 may be circular cylindrical although the working zone
surface may comprise a polygonal cylindrical configuration or other
shaped surface in further examples. Moreover, as shown, the working
zone surface 217 has a length L extending along a rotation axis 219
of the forming roll 207. The forming rolls of the disclosure
further include at least one thermal resistance boundary extending
at an acute angle relative to the rotation axis of the forming
roll. For example, as shown in the figures, the at least one
thermal resistance boundary can comprise a first thermal resistance
boundary extending at an acute angle .alpha. relative to the
rotation axis of the forming roll and a second thermal resistance
boundary extending an another acute angle .beta. relative to the
rotation axis of the forming roll. As shown, the acute angles
.alpha., .beta. may be identical to one another and facing opposite
directions in some examples although the acute angles may be
different in further examples. The acute angles .alpha., .beta. may
have an absolute value within a range of from about 30.degree. to
about 60.degree. although other acute angles may be provided in
further examples. Providing acute angles .alpha., .beta. that are
opposite to one another can help generate a circumferential
dovetail portion with a trapezoidal cross-sectional portion 401
shown in FIG. 4.
[0049] As shown in FIG. 4, the first and second thermal resistance
boundaries may be provided at respective end portions 403, 405 of
the forming roll to allow heat to be more effectively retained
within the working zone portion 215. Indeed, the thermal resistance
boundary provides a location of relatively higher thermal
resistance to heat transfer from the working zone portion, thereby
helping inhibit heat transfer out of the working zone portion 215
and into the end portions 403, 405 of the forming roll 207.
Meanwhile, the angles .alpha., .beta. of the thermal resistance
boundaries can provide desirable thermal distribution
characteristics of the working zone portion 215. Indeed, by
providing the thermal resistance boundary at opposite acute angles
.alpha., .beta. relative to the rotation axis of the forming roll
207, the illustrated circumferential dovetail portion with a
trapezoidal cross-sectional portion 401 may be provided such that
heat from the stream of molten glass 205 is retained and
appropriately distributed throughout the working zone portion 215.
The resulting heat distribution in the working zone portion 215
provides a desirable temperature distribution profile that results
in substantial uniform radial expansion of the working zone surface
217 relative to the rotation axis 219 across the length L of the
working zone surface 217 in response to heating of the working zone
portion 215 by the molten glass 205 from a first temperature to a
second temperature. Due to the substantial uniform radial expansion
of the working zone surface 217 during heating, the working zone
surface 217 can maintain a substantially uniform radius across the
length L of the working zone surface 217 throughout heating and
cooling cycles of the forming roll 207.
[0050] The thermal resistance boundary may comprise a wide range of
alternative configurations. For example, FIG. 4 illustrates a first
thermal resistance boundary comprising a first frustoconical groove
407 and a second thermal resistance boundary comprising a second
frustoconical groove 409. Each frustoconical groove 407, 409 can be
defined in the forming roll 207 to extend at the respective acute
angles .alpha., .beta. relative to the rotation axis 219 of the
forming roll 207. The frustoconical grooves 407, 409 can extend
completely, partially, or intermittently around the circumference
of the forming roll 207. For example, as shown, the frustoconical
grooves 407, 409 each extend continuously and completely about the
periphery of the forming roll 207. Providing one or both of the
frustoconical grooves as a continuous frustoconical groove that
extends completely about the periphery of the forming roll can
provide a more efficient boundary to thermal conduction outside the
working zone portion. One or both of the frustoconical grooves may
alternatively comprise discontinuities, such as aligned groove
segments that are spaced apart about the periphery of the forming
roll 207. While the discontinuities may provide points of reduced
thermal resistance, the discontinuities may provide structural
integrity to the forming roll that may not otherwise be achieved by
a continuous frustoconical groove.
[0051] As further illustrated in FIG. 4, the frustoconical grooves
407, 409 can extend a depth "d" into the working zone surface 217.
Various depth ranges may be provided to provide a sufficient
thermal resistance boundary while maintaining the structural
integrity of the forming roll 207. For example, as shown, the
forming roll can include a diameter "D" that is twice the radius
"R" of the forming roll 207. The depth "d" of the frustoconical
grooves 407, 409 can be within a range of from about 50% to about
85% of the radius "R" of the forming roll 207 although other depths
may be provided in further examples.
[0052] As further shown in FIGS. 2-4, the roll forming apparatus
201 may also comprise a pair of gap rings 221, 223, wherein the
forming roll 207 and the forming body 209 are spaced from each
other by the pair of gap rings 221, 223 to define the glass forming
gap 211. While the thermal resistant boundaries of the forming roll
207 and the forming body 209 are configured to maintain a
substantially uniform width W along length L during radial
expansion of the forming roll and forming body, the gap rings 221,
223 may be configured to maintain a substantially constant width W
during this radial expansion. In the example shown in FIGS. 2-4,
the gaps rings 221, 223 are mounted to the working zone portion 215
of the forming roll 207 and protrude from the working zone surface
217 by a distance X. In alternative examples, one or both of the
gap rings 221, 223 may be mounted to a working portion 225 of the
forming body 209 and protrude from a working zone surface 227 of
the working portion 225 by a distance X. In further examples, as
further shown by the gap rings 222, 224 in hidden lines in FIG. 2,
both the forming roll 207 and the forming body 209 may each include
a pair of gap rings that each extend from the corresponding working
zone surface 217, 227 by a distance X/2. Respective gap rings 221,
222 and 223, 224 can engage one another in operation such that the
total spacing of the working zone surfaces 217, 227 provided by the
gap rings is X.
[0053] Thus, the pair of gap rings 221, 223 can ensure that, during
expansion, the working zone surfaces 217, 227 of the forming roll
207 and the forming body 209 will remain separated by a constant
width W that corresponds to the distance X. Accordingly, a pair of
gap rings 221, 223 may be selected that protrude from the working
zone surface 217 by a predetermined distance X to form a glass
ribbon 213 having a substantially uniform thickness T that
corresponds to the predetermined distance X. As such, thin glass
ribbons with a uniform thickness of 1 mm or less can be easily
formed without having to predict how the width W may change during
the expansion of forming rolls absent the use of gap rings.
Moreover, even though the gap rings 221, 223 may themselves expand
as they rise in temperature during the roll forming process, the
expansion of distance X should be nominal when distance X is small
(as is the case when forming thin glass sheets of 1 mm or less).
Furthermore, the gap rings 221, 223 may be coated with a low
thermal conductivity ceramic coating or they may comprise a
material having a low coefficient of thermal expansion to reduce
the effects of heat on the expansion of distance X.
[0054] The pair of gaps rings 221, 223 may be integral with the
forming roll 207 and/or forming body 209 or they may be mounted
separately to the forming roll 207 and/or forming body 209.
Additionally, as discussed above, there may be a second pair of gap
rings (not shown) mounted to the forming body 209 that contact the
first pair of gap rings 221, 223 on the forming roll 207. Moreover,
although the example provided shows a pair of gaps rings 221, 223
mounted on the working zone portion 215 of forming roll 207, they
can alternatively be mounted to the end portions 403, 405 of the
forming roll 207. However, since the working zone portion 215 will
retain heat from the stream of molten glass 205 and therefore
expand at a rate different from (and greater than) the end portions
403, 405, mounting the gap rings 221, 223 on the working zone
portions 215, 225 can lead to a better control of the width W along
length L. In other words, mounting the gap rings 221, 223 to the
end portions 403, 405 will ensure that the end portions 403, 405
remain a constant distance apart but may not ensure that the
working zone surfaces 217, 227 will remain a constant distance
apart since the working zone surfaces 217, 227 may expand at a rate
different from the end portions 403, 405.
[0055] As shown in FIG. 4, each of the forming roll 207 and the
forming body 209 may have a similar (such as the illustrated
identical) thermal resistance boundary configuration. In fact, as
discussed above, the forming body 209 may be identical to the
forming roll 207 such that the forming roll 207 and the forming
body 209 form a pair of substantially identical forming rolls as
shown. One or both of the forming roll and forming body may have
alternative constructions for the thermal resistance boundaries.
For example, one or both of the forming roll 207 and/or the forming
body 209 can comprise the forming roll 501 shown in FIGS. 5 and 6.
The forming roll 501 comprises a working zone portion 503
comprising a working zone surface 505 for engaging the stream of
molten glass 205. The working zone surface 505 including a length L
extending along a rotation axis 507 of the forming roll 501. As
shown in FIG. 6, the forming roll 501 includes a first thermal
resistance boundary comprising a first frustoconical end surface
601 and a second thermal resistance boundary comprising a second
frustoconical end surface 603. Each frustoconical end surface 601,
603 can extend at the respective acute angles .alpha., .beta.
relative to the rotation axis 507 of the forming roll 501.
[0056] As further illustrated in FIG. 6, the frustoconical end
surfaces 601, 603 can extend a depth "d" into the working zone
surface 505. Various depth ranges may be provided to provide a
sufficient thermal resistance boundary while maintaining the
structural integrity of the forming roll 503. For example, as
shown, the forming roll can include a diameter "D" that is twice
the radius "R" of the forming roll 503. The depth "d" of the
frustoconical end surface 601, 603 can be within a range of from
about 50% to about 85% of the radius "R" of the forming roll 503
although other depths may be provided in further examples.
[0057] As shown in FIG. 6, the end surface 601, 603 do not face a
corresponding surface of end portions 605, 607 of the forming roll
501. As such, the thermal resistance boundaries of FIGS. 5 and 6
may have a higher thermal resistance to heat transfer than the
thermal resistance boundaries of FIGS. 2-4. Although not shown, the
forming roll 501 may optionally include a plurality of
strengthening ribs extending radially about the rotation axis 507
and spanning between the end surfaces 601, 603 and the respective
end portions 605, 607 to increase the structural strength of the
forming roll 501.
[0058] In further examples, one or both of the forming roll and
forming body can comprise the forming roll 701 shown in FIGS. 7 and
8. The forming roll 701 comprises a working zone portion 703
comprising a working zone surface 705 for engaging the stream of
molten glass 205. The working zone surface 705 including a length L
extending along a rotation axis 707 of the forming roll 701. The
forming roll 701 includes a first thermal resistance boundary
comprising a first plurality of bores 709 and a second thermal
resistance boundary comprising a second plurality of bores 711. As
indicated by the hidden lines 713 of each bore 715, the bores can
extend along a bore axis 801 (see FIG. 8) at the respective acute
angles .alpha., .beta. relative to the rotation axis 707 of the
forming roll 701 as indicated by frustoconical sectional planes
8-8. FIG. 8 illustrates the array of bores 715 radially spaced
about the rotation axis 707 of the forming roll 701 along
corresponding frustoconical planes 8-8 of FIG. 7. The bores 715 may
or may not be equally spaced from each other. Additionally, the
bores 715 may vary in number, depth, and size from the example
shown. In these alternative embodiments, as each bore axis 801
extends at the respective acute angles .alpha., .beta., the thermal
resistant boundaries similarly extend at acute angles relative to
the rotation axis of the forming roll 701. Providing the thermal
resistance boundaries as respective pluralities of bores can
provide enhanced structural integrity when compared to other
designs that remove substantial portions of the forming roll to
create the thermal resistance boundaries.
[0059] In still further examples, one or both of the forming roll
and forming body can comprise the forming roll 901 shown in FIGS. 9
and 10. The forming roll 901 comprises a working zone portion 903
comprising a working zone surface 905 for engaging the stream of
molten glass 205. The working zone surface 905 including a length L
extending along a rotation axis 907 of the forming roll 901. The
forming roll 901 includes a first thermal resistance boundary
comprising a first frustoconical groove 909 and a second thermal
resistance boundary comprising a second frustoconical groove 911.
Each frustoconical groove 909, 911 can be defined in the forming
roll 901 to extend at the previously described respective acute
angles .alpha., .beta. relative to the rotation axis 907 of the
forming roll 901. As with the frustoconical grooves 407, 409
illustrated in FIG. 4, the frustoconical grooves 909, 911 can
extend completely, partially, or intermittently around the
circumference of the forming roll 901. For example, as shown, the
frustoconical grooves 909, 911 each extend completely about the
periphery of the forming roll 901. Providing one or both of the
frustoconical grooves as a frustoconical groove that extends
completely about the periphery of the forming roll 901 can provide
a more efficient boundary to thermal conduction outside the working
zone portion.
[0060] Optionally, one or both of the frustoconical grooves may
alternatively comprise discontinuities to increase the structural
integrity of the forming roll that may not otherwise be achieved by
the continuous frustoconical groove. For example, as shown in FIG.
10, each of the frustoconical grooves 909, 911 may include a
plurality of strength elements, such as the illustrated weld points
1001, 1003, positioned within the groove to strengthen the forming
roll 901. The weld points 1001, 1003 attach the working zone
portion 903 to end portions 913, 915 of the forming roll 901, thus
adding strength and rigidity to the forming roll 901. The weld
points 1001, 1003 can extend completely or partially around the
circumference of the forming roll 901. There can also be more than
one weld point positioned within each groove. Moreover, the weld
points 1001, 1003 can be positioned radially so that they are
closer to the surface of the forming roll 901 or they can be
positioned deeper within the grooves so that they are closer to the
rotation axis of the forming roll 901.
[0061] The forming rolls of the disclosure may also include an
optional cooling passage. For example, as shown in FIG. 10, the
forming roll 901 includes an optional cooling passage 1007
configured to provide fluid cooling to the forming roll 901. In
some examples, the cooling passage 1007 may be coaxial with the
forming roll 901 and extends through the working zone portion 903.
As further illustrated in FIG. 10, the frustocontical grooves 909,
911 can extend a depth "d" into the working zone surface 905.
Various depth ranges may be provided to provide a sufficient
thermal resistance boundary while maintaining the structural
integrity of the forming roll 903. For example, as shown, the
forming roll can include a diameter "D" that is twice the radius
"R1" of the forming roll 903. Moreover, the cooling passage 1007
can include a radius "R2" wherein a wall thickness "WT" is formed
between the working zone surface 905 and the interior wall surface
of the cooling passage 1007. The depth "d" of the frustoconical
grooves 909, 911 can be within a range of from about 50% to about
85% of the wall thickness "WT" of the forming roll 903 although
other depths may be provided in further examples.
[0062] Cooling fluid may be supplied to this cooling passage 1007
an dispersed as a cooling fluid stream 1009 to cool the forming
roll 901 and reduce its expansion during the roll forming process.
The cooling fluid may be water or compressed air or some other
cooling fluid. As shown in FIG. 10, a conduit 1005 may be provided
within the cooling passage 1007 to deliver the cooling fluid and
direct the cooling fluid stream 1009 against an internal central
portion of the forming roll 901.
[0063] During the roll forming process, the central portion of the
forming roll 901 experiences a greater amount of heat than the
outer peripheral portions of the forming roll 901. Thus, by
directing the cooling fluid towards the central portion of the
forming roll 901, the temperature of the central portion can be
controlled so that the central portion expands at a rate
substantially uniform to outer peripheral portions of the working
zone portion 903. Accordingly, directing the fluid stream 1009
against an internal central portion of the forming roll 901 can
facilitate substantial uniform expansion of the working zone
surface 905 across the length L of the working zone surface 905 in
response to heating of the working zone portion 903 by the stream
of molten glass 205.
[0064] In addition or in alternative to flowing a cooling fluid
through a cooling passage, heat H may be directed to outer
peripheral edges of the working zone portion 903 to facilitate
substantial uniform expansion of the working zone surface 905
across the length L of the working zone surface 905 in response to
heating of the working zone portion 903 by the molten glass, as
shown in FIG. 10. By directing heat towards the outer peripheral
edges of the working zone portion 903, the temperature of the outer
peripheral portions can be controlled so that the outer peripheral
portions expand at a rate substantially uniform to the central
portion of the working zone portion 903.
[0065] Methods of forming the glass ribbon 213 will now be
described and can apply to any of the example forming roll/forming
body configurations of the disclosure. The method can be carried
out with at least one forming roll and a forming body spaced to
define a glass forming gap between the forming roll and forming
body. As mentioned previously, the forming body can comprise
various configurations and may be similar or identical to the
forming roll. For example, as shown in FIGS. 2 and 4, both the
forming roll 207 and the forming body 209 including working zone
portions 215, 225 comprising the working zone surfaces 217, 227
including the length L extending along the rotation axis 219 of the
corresponding forming roll 207 and forming body 209. As mentioned
previously, the forming roll and forming body can each include the
thermal resistance boundary comprising the frustoconical grooves
407, 409 defined in the forming roll 207 that each extend at the
acute angle .alpha., .beta. relative to the respective rotation
axis (e.g., rotation axis 219). The method can provide the acute
angles .alpha., .beta. within a range of from about 30.degree. to
about 60.degree. although other acute angles may be used in further
examples.
[0066] As discussed previously, other thermal resistance boundary
configurations may be used in further examples. For instance, FIGS.
5 and 6 illustrate the thermal resistance boundary comprising the
frustoconical end surface 601, 603 of the working zone portion 503.
FIGS. 7 and 8 illustrated another example wherein the thermal
resistance boundary comprises the plurality of bores 709, 711
spaced radially about the rotation axis 707 of the forming roll. As
shown in FIGS. 9 and 10, another examples provides the thermal
resistance boundary as the frustoconical groove 909, 911 with the
plurality of strength elements (e.g., weld points 1001, 1003)
positioned within the groove.
[0067] Turning to FIGS. 2 and 3, the methods can further include
the steps of supplying the stream of molten glass 205 and feeding
the stream of molten glass through the gap 211 to form the glass
ribbon 213 including the formed thickness T. The thermal resistance
boundary of each example of the disclosure facilitates substantial
uniform radial expansion of the working zone surface relative to
the rotation axis across the length of the working zone surface in
response to heating of the working zone portion by the molten
glass. In one example, the method can further include the step of
cooling the forming roll with a fluid. For instance, as shown in
FIG. 10, the method can include flowing the fluid through the
cooling passage 1007 extending along the rotation axis 907 of the
forming roll 901. As further shown, the method can include the step
of cooling by flowing the fluid against the internal central
portion of the forming roll, for example, by way of the cooling
fluid stream 1009. Flowing the fluid against the internal central
portion of the forming roll can facilitate substantial uniform
expansion of the working zone surface 905 across the length L of
the working zone surface 905 in response to heating of the working
zone portion 903 by the molten glass 205.
[0068] As further shown schematically by "H" in FIG. 10, the method
can also include the step of heating the outer peripheral edges of
the working zone portion 903 to facilitate substantial uniform
expansion of the working zone surface 905 across the length L of
the working zone surface 905 in response to heating of the working
zone portion 903 by the molten glass 205.
[0069] It will be apparent to those skilled in the art that various
modifications and variations can be made without departing from the
spirit and scope of the claimed invention.
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